Electrical connector and method



Aug. 14, Q BERG ELECTRICAL CONNECTOR AND METHOD Filed Jan. 13, 1953lNVNTOR pas/v77 552 United States Patent Oflice 2,759,161 Patented Aug.14, 1956 ELECTRICAL CONNECTOR AND METHOD Quentin Berg, New Cumberland,Pa assignor to Aircraft- Marine Products -Ine., Harrisburg, Pa.

Application January 13, 1953, Serial No. 330,974

3 Claims. (Cl. 339-97) This invention relates to electrical connectors,and more particularly to electrical connectors provided with one or moreinsulation-piercing members whereby they may be attached to theunstripped ends of insulated electrical conductors and brought intoelectrically conductive relation thereto by means of suchinsulation-piercing members.

In the past solderless connectors of the insulation-piercing type havehad only a limited field of use because it has not been feasible toattain a stable low resistance connection for the heavier .currentloads, and soldering of the connection obviously was not feasiblebecause of the presence of the insulation.

An object of the present invention is to provide an insulation-piercingconnector and a process of making and applying it which will makeavailable the advantages of a soldered connection without the necessityof stripping insulation from insulated wire. Another object is toprovide an insulation-piercing connector constructed so that it can beapplied merely with pressure and heat without handling any separatesolder or soldering tool; and the resultant connection will be securelysoldered between the insulation-piercing part of the connector and theelectrical conductor.

In the drawings:

Figure 1 is a perspective view of a completed connection embodying myinvention;

Figure 2 is a sectional view taken on line 22 of Figure 1;

Figure 3 is a view in transverse section of the blank with partiallypreformed ferrule from which the connection of Figures 1 and 2 isformed;

Figure 4 is a perspective view of another form of completed terminalembodying the invention applied to an insulated conductor;

Figure 5 is a sectional view through the completely crimped connectorand conductor taken .on line S5 of Figure 4;

Figure 6 is a perspective view of the blank from which the connection ofFigures 4 and 5 is made, with partially preformed ferrule-formingportion.

As shown in Figures 1 and 2 the connector consists of a ferrule portion10 made of malleable sheet metal, advantageously pure electrical copperor brass. This sheet metal is formed to a cylindrical shape embracingand tightly compressing the wire within it. The connector in thisinstance is shown as consisting only of a ferrule, but it will beunderstood that any desired tongue or connector ferrule or other partmay be attached or made integral therewith. A portion 12 had beenpunched and turned in with one side still attached as shown;this'portion is formed to a sharp edged or pointed conductor-engagingprong which, as shown, is pushed through the insulation 14 on the wireand into contact with the central conductor 16 of the wire. Thisstructure is more particularly described and claimed in my copendingapplication Serial No. 142,511 filed February 4, 1950.

The insulation piercing member 12 is provided on its sides, for asubstantial distance back from and adjacent its point, with a coating ofsolder 18, i. e., a low melting point electrically conductive solidwhich readily wets and adheres strongly to both the metal prong 12 andthe conductor 16. This may be one of the lower melting point solderscommonly used in this art for making electrical connections; butadvantageously is one which has its melting point lowered and itswetting power enhanced by indium included in the alloy, as availablefrom the Indium Corporation of America.

In use the insulated conductor is inserted laterally into the open sideof the connector as shown in Figure 3 and against the prong 12. Theconnector is then closed onto the wire and compressed in crimping dies,e. g. according to practice already well known in this art exceptingthat in this instance the portion of the die which engages the base 20of the prong 12 is strongly heated by means such as block 22 which inturn is heated by inductance coil 23 as indicated in Figure 2 at theinstant when the prong 12 is piercing into the central conductor 16,whereby heat is conducted along the prong to the solder coating 18,which is thereby fused in contact with the wire 16. The fused solderwets the wire and flows along it, thus forming a secure bond, andextruded areas of electrical con duction which are sealed againstcorrosion.

Instead of providing a heating element in the die, the crimpedconnection may be heated after crimping by an external heater, or byhigh frequency internal heating such as inductance coil 31 shown inFigure 4 or a strong overload current may be passed through thecompleted connectiim such as is indicated in Figure 1, with overloadcurrent passing from clamp 13 to clamp 15, in the die or after it isremoved therefrom, thus causing heating at the points of contact withthe wire and thereby to fuse the solder and bond the connector to thewire. With this internal heating, whether by induction or resistanceheat-ing of the contact surfaces, higher melting solder alloys or evenpure tin may be used because the heat is localized on the solder-and isless likely to do serious damage to the insulation; the heating in suchcase should be continued just long enough tofuse the solder and heatabove its fusion point the surfaces which are to be bonded.

Figures 4, 5 and 6 show the application of the invention to anotherinsulation piercing connector of the type covered by the patent to MacyNo. 2,557,126.

The connector blank, as shown, comprises a connecting tongue portion 24and a ferrule portion 10a from one side of which extend ears 12a and 12bslightly taper ing and long enough to be curled on a radius shorter thanthat of the wire to curl in through the insulation for engaging thecentral conductor. They are wide enough and thick enough to give therigidity required to push them through the insulation while supportedbythe die as shown in Figures 13 and 14 of said patent; and to give thecontact area and conductive cross-section required for low resistanceconduction of the rated current. An car 30 is designed to wrap aroundthe Wire and hold it fully in the embrace of the connector. The ears 30and 12a are separated sufiicieutly to receive the opposite ear 12bbetween them when the blank is applied to an insulated conductor. Thisslightly tapering ear 12b extends from the other side of the blankopposite the space 32 and leaving ferrule edges 36 and 38 opposite theears 12a and 30.

Although the connecting tongue portion 24 of the blank is shown as atypical ring tongue for use with a binding post or screw, it will beunderstood that this portion of the terminal may be given any desiredform or omitted entirely.

This terminal is applied to the wire in a manner, and

by, use of special crimping dies, such as are shown and,

described in the Macy patent hereinabove identified. The ferrule part ofthe connector is crimped upon an unstripped part of an insulatedconductor, the ear 30 is crimped about the insu1ation14 to securely gripthe insulation throughout its circumference, while the ears 12a and 12bare curled by the crimping die to shorter radius and driven endwise intoand through the insulation so as to make contact with the strandedconductor core of the wire 16, as shown in Figures 4 and 5. It is atthis point that the present invention is brought into play.

As will 'be seen from an inspection of Figures 1 to 4 and 6, theinsulation-piercing tips of the ears 12a and 12b are each provided withan excess coating 18 of a.

solder suitable for soldering together said tips and the conductor 16and in amount suflicient to flow into and along the capillary spaceswhere the ears touch the wire 16. Such a solder, for example, for usewith connectors made ofcopper or alloys thereof which are to be solderedto conductors 16, also made of copper or alloys thereof, isadvantageously one of those which is fusible below the softening anddecomposition temperatures of the insulation on the connector or on thewire, e. g. below about 150 C. Such a solder may consist of 37.5% lead,37.5% tin and 25% indium or other low melting alloy with suitableadditions of indium to improve its melting power and bond strength. Suchlow temperature fusible alloys, e. g., Woods metal, Lipowitz metal andmodifications of such metals may also be used without indium, eventhough they would not give sufiicient bond strength for ordinarysoldered connections. Because the solder is within a pressure crimpedconnection such strength is not required. In some cases (e. g. withasbestos or fiber glass insulation) much higher temperatures can betolerated and ordinary solders and even hard solder brazing alloys canbe used. This solder may be applied to the insulation-piercing ears 12aand 12b in any convenient manner, as, forexample, by dipping these carsinto a bath of molten solder, by sprayingthe solder on the tips of theears, by electroplating them with the solder or by any other suitablemetal coating method known to the art. v p

, The connector, provided withpthesolder coated insulation-piercing ears12a, 12b, having been crimped upon the insulated conductor, as shown inFigures 4 and 5, with the ears 12a and 12b penetrating the stranded Wire16, it is necessary to effect a fusion of the solder to pro-, duce asoldered joint between the ends of the ears 12a and 12b and theconductor 16. Such fusion may be effected in various ways, as, forexample, by heating the bases 20aof the ears 12a and 12b while theferrule is under pressure in the crimping dies, to a temperature abovethe fusion temperature of the solder sothat the heat conducted throughthe earsduring the final stage of the crimping eifects a sufficientfusion of the solder to insure a soldered joint, or, a'quick heating,effecting fusion of the solder by causing a current to flow through thisconnection as the contact is made between the cars 12a and 12b and theconductor 16 during crimpingor after crimping is completed-as, forexample, by con: necting the ferrule and wire respectively to oppositeplates of a charged condenser, so that it discharges a heavy but briefcurrent through the points of contact of the ears 12a and 12b with theconductor 16. This latter method is claimed in an application of WilliamS. Watts, attorneys docket 121617.

From the foregoing description it will be seen that, not only is themechanical strength of the connection between .the connector and theinsulated conductor increased, but, by reason ofthe soldered connectionbetween the ears 12a and 12b and the conductor 16, higher electrical'conductivity and corrosion resistance is achieved.

I claim:

1. An electrical connector for effecting an electrical and mechanicalconnection with an insulated conductor having a stranded metallic corecomprising a ferrule adapted to be crirnped about an insulated portionof the conductor, insulation-piercing prong means disposed on saidferrule soas to be driven through the conductor insulation and betweenthe core strands uponcrimping said ferrule, said prong means being:coated with solder for electrically and mechanically bonding said meansto the core strands upon application of heat thereto after crimping ofthe connector.

2. The method of forming an electrical connection between a strandedinsulated conductor and a connector having a ferrule with insulationpiercing prong means thereon, including the steps. of coating the prongmeans with a solder-type bonding material, crimping the ferrule aboutthe insulated conductor. and driving the prong means through theinsulation and into the conductor core between the strands thereof, andheating at least the bonding material for causing the solder to flow andupon cooling to unite mechanically and electrically the strands andprong means.

. 3. In an electrical connection, a stranded electrical conductor havingan insulation sheath thereon, an electrical connector including aferrule embracing said conductor, insulation piercing means integrallyextending from said ferrule through said sheath and into the conductorstrands, and a solder-type bonding material mechanically andelectrically uniting said strands and said piercing means.

ReferencesCited in the file of this patent UNITED STATES PATENTS1,390,596 Thornton Sept. 13, 1921 1,875,241 Idank Aug. 30, 19322,494,137 Martines Jan. 10, 1950 2,501,870 Malhiot Mar. 28, 19502,557,126 Macy June 19, 1951 2,655,641 Asoif Oct. 13, 1953 2,680,235Pierce June 1, 1954 FOREIGN PATENTS 472,582 Great Britain Sept. 27, 1937

